UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

FORM 10-Q

For the quarterly period ended March 31, 2005

OR

Commission File Number 000-49755

QUINTON CARDIOLOGY SYSTEMS, INC.

3303 Monte Villa Parkway
Bothell, Washington 98021
(Address of principal executive offices)

(425) 402-2000
(Registrant’s telephone number)

     Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports) and (2) has been subject to such filing requirements for the past 90 days. YES þ    NO o

     Indicate by check mark whether the registrant is an accelerated filer (as defined in Rule 12b-2 of the Exchange Act). YES þ    NO o

     The number of shares outstanding of the registrant’s common stock as of May 3, 2005 was 14,083,730.

TABLE OF CONTENTS

2

PART I — FINANCIAL INFORMATION

Item 1. Financial Statements

QUINTON CARDIOLOGY SYSTEMS, INC. AND SUBSIDIARIES
UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS

The accompanying notes are an integral part of these unaudited condensed consolidated financial statements.

3

QUINTON CARDIOLOGY SYSTEMS, INC. AND SUBSIDIARIES
UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

The accompanying notes are an integral part of these unaudited condensed consolidated financial statements.

4

QUINTON CARDIOLOGY SYSTEMS, INC. AND SUBSIDIARIES
UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

The accompanying notes are an integral part of these unaudited condensed consolidated financial statements.

5

QUINTON CARDIOLOGY SYSTEMS, INC. AND SUBSIDIARIES

NOTES TO UNAUDITED CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

1. Organization and Description of Business

     Quinton Cardiology Systems, Inc. (“QCS”) is a Delaware corporation. QCS and its subsidiary, Quinton Cardiology, Inc. (“Quinton”) and its majority owned subsidiary Shanghai Quinton Medical Device Co., Ltd. (“Shanghai-Quinton”) are referred to herein as the Company. The Company develops, manufactures, markets and services a family of advanced cardiology products used in the diagnosis, monitoring and management of patients with heart disease.

2. Summary of Significant Accounting Policies

     Basis of Presentation

     The condensed financial statements present the Company on a consolidated basis. All significant intercompany accounts and transactions have been eliminated. The condensed consolidated balance sheet dated March 31, 2005, the condensed consolidated statements of operations for the three-month periods ended March 31, 2004 and 2005 and the condensed consolidated statements of cash flows for the three-month periods ended March 31, 2004 and 2005 have been prepared by the Company and are unaudited. The condensed consolidated balance sheet dated December 31, 2004 was derived from audited financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America have been omitted pursuant to the rules and regulations of the Securities and Exchange Commission. The notes to the audited consolidated financial statements included in the Company’s annual report on form 10-K for the fiscal year ended December 31, 2004 provide a summary of significant accounting policies and additional financial information that should be read in conjunction with this report. In the opinion of management, all adjustments, consisting only of normal recurring adjustments, necessary to present fairly the financial position of the Company for the interim periods, have been made. The results of operations for such interim periods are not necessarily indicative of the results for the full year or any future period.

     Certain prior year amounts have been reclassified to conform to current period presentation.

     Use of Estimates

     The preparation of financial statements and related disclosures in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and revenues and expenses during the periods reported. These estimates include but are not limited to estimates assessing the collectability of accounts receivable, the salability and recoverability of inventory, the adequacy of warranty liabilities, the realizability of investments, the calculation of our effective tax rate, the impairment of long-lived assets, the likelihood of closing on a potential business combination and the useful lives of tangible and intangible assets. The market for the Company’s products is characterized by intense competition, rapid technological development and frequent new product introductions, all of which could affect the future realizability of the Company’s assets. The Company reviews estimates and assumptions periodically, and the effects of revisions are reflected in the consolidated financial statements in the period they are determined to be necessary. Actual results could differ from these estimates.

     Recent Accounting Pronouncements

     In December 2004, the Financial Accounting Standards Board (“FASB”) issued Statement of Financial Accounting Standards No. 123 (revised 2004), “Share-Based Payment” (“SFAS No. 123R”). SFAS No. 123R requires the Company to measure the cost of employee services received in exchange for an award of an equity instrument, such as stock options, based on the grant-date fair-value of the award. The associated cost must be recognized over the period during which an employee is required to provide service in exchange for the award (usually the vesting period). In April 2005, the U.S. Securities and Exchange Commission adopted a new rule amending the compliance dates for SFAS No. 123R. In accordance with the new rule, the accounting provisions of SFAS No. 123R will be effective for the Company in the first

6

quarter of 2006. SFAS No. 123R provides for a variety of implementation alternatives, including accounting for the change prospectively or restating previously reported amounts to reflect the compensation expense that would have been recorded under SFAS No. 123R. The Company is in the process of evaluating the impact of adopting SFAS No. 123R and of determining the impact on its results of operations and statements of cash flows.

     Net Income Per Share

     In accordance with SFAS No. 128, “Computation of Earnings Per Share,” basic income per share is computed by dividing net income by the weighted average number of shares of common stock outstanding during the period. Diluted income per share is computed by dividing net income by the weighted average number of common and dilutive potential common shares outstanding during the period. Potential common shares consist of shares issuable upon the exercise of stock options using the treasury stock method. Potential common shares are excluded from the calculation if their effect is antidilutive.

     The following table sets forth the computation of basic and diluted net income per share:

     For the three-month periods ended March 31, 2004 and 2005, 25,000 and 75,000, respectively, of shares issuable upon exercise of stock options were excluded from the computation of diluted income per share as their impact was antidilutive.

     Accounting for Stock-Based Compensation

     The Company has elected to apply the disclosure-only provisions of SFAS No. 123, “Accounting for Stock-Based Compensation” (“SFAS No. 123”). In accordance with the provisions of SFAS No. 123, the Company applies Accounting Principles Board Opinion No. 25, “Accounting for Stock Issued to Employees,” and related interpretations in accounting for its stock option plans. The Company accounts for stock options issued to non-employees in accordance with the provisions of SFAS No. 123 and Emerging Issues Task Force consensus on Issue No. 96-18, “Accounting for Equity Instruments That are Issued to Other Than Employees for Acquiring, or in Conjunction with Selling, Goods or Services.”

     Had compensation cost been determined based on the fair value of the option awards at the grant dates during the three-month periods ended March 31, 2004 and 2005, consistent with the provisions of SFAS No. 123, the Company’s reported net income would have been the pro forma amounts indicated below:

7

     The following table sets forth, consistent with the provisions of SFAS No. 123, the denominator for calculating pro forma diluted net income per share for each respective period:

     The Company calculated the fair value of each option grant on the date of grant using the Black-Scholes option-pricing model. The following assumptions were used for each respective period:

          Goodwill

     Goodwill represents the excess of costs over the estimated fair values of net assets acquired in connection with our acquisitions of a medical treadmill manufacturing line in 2002 and Spacelabs Burdick, Inc. (“Burdick”) in 2003, which, in accordance with SFAS No. 142, “Goodwill and Other Intangible Assets,” (“SFAS No. 142”) are not being amortized. Also in accordance with SFAS No. 142, the Company tests goodwill for impairment at the reporting unit level on an annual basis and between annual tests in certain circumstances. The Company has determined that it has two reporting units, consisting of general cardiology products, which includes the service business, and the Shanghai-Quinton joint venture, both of which operate in the cardiology market and have similar economic and operating characteristics.

     SFAS No. 142 requires a two-step goodwill impairment test whereby the first step, used to identify potential impairment, compares the fair value of a reporting unit with its carrying amount including goodwill. If the fair value of a reporting unit exceeds its carrying amount, goodwill of the reporting unit is considered not impaired, thus the second step of the goodwill impairment test used to quantify impairment is unnecessary. Management has estimated that the fair

8

values of the Company’s reporting units to which goodwill has been allocated exceed their carrying amounts, and as a result, the second step of the impairment test, which would compare the implied fair value of the reporting unit goodwill with the carrying amount of that goodwill, was unnecessary for the periods presented.

     Intangible Assets and Other Long-Lived Assets

     The Company’s intangible assets are comprised primarily of a trade name, developed technology and customer relationships, all of which were acquired in our acquisition of Burdick in 2003. Company management uses judgment to estimate the useful lives of each intangible asset. The Company believes the Burdick trade name has an indefinite life, and accordingly does not amortize the trade name. Developed technology was assigned a seven year useful life, based on the estimated remaining economic life of the related products. The useful life of the distributor relationships has been determined to be 10 years, based on historical turnover experience and in consideration of the long standing and stable nature of these relationships.

     The Company annually re-evaluates its conclusion that the Burdick trade name has an indefinite live and makes a judgment about whether there are factors that would limit the ability to benefit from the trade name in the future. If there were such factors, the Company would amortize the trade name. Company management annually reviews the trade name intangible asset for impairment by comparing the fair value of the asset to its carrying value. The Company uses judgment to estimate the fair value of the trade name. The judgment about fair value is based on expectations of future cash flows and an appropriate discount rate.

     In accordance with Statement 144, long-lived assets, such as property, plant, and equipment, and intangibles subject to amortization, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated future cash flows, an impairment charge is recognized on our statement of operations and as a reduction to the asset by the amount by which the carrying amount of the asset exceeds the fair value of the asset. Assets to be disposed of would be separately presented in the balance sheet and reported at the lower of the carrying amount or fair value less costs to sell, and are no longer depreciated. The assets and liabilities of a disposal group classified as held for sale would be presented separately in the appropriate asset and liability sections of the balance sheet.

     The Company recorded amortization expense for identifiable intangibles of $81,000 in each of the three-month periods ended March 31, 2004 and 2005.

3. Inventories

     Inventories were valued at the lower of cost, on an average cost basis, or market and were comprised of the following:

4. Credit Facility

     The Company established a line of credit in December 2002. Borrowings under the line of credit are currently limited to the lesser of $12,000,000 or an amount based on eligible accounts receivable and eligible inventories. Substantially all of the Company’s assets are pledged as collateral for the line of credit. This line of credit bears interest based on a variable rate ranging from the bank’s prime rate plus a minimum of 0.0% to a maximum of 0.5% based on a funded debt to Earnings Before Interest, Taxes, Depreciation, and Amortization (“EBITDA”) ratio, which amounted to 5.25% and 5.75% at December 31, 2004 and March 31, 2005, respectively. In addition, unused balances under this facility bear monthly

9

fees equal to 0.25% per annum on the difference between the maximum credit limit and the sum of (i) the average daily principal balance during the month and (ii) the face amount of any letters of credit. The current line of credit expires on December 30, 2005. At December 31, 2004 and March 31, 2005, the Company did not have any borrowings under this line of credit. As of March 31, 2005, the Company had capacity to borrow $9,049,000 based on eligible accounts receivable and eligible inventory. The credit facility contains standard negative covenants and restrictions on actions by the Company, including but not limited to, activity related to common stock repurchases, liens, investments, capital expenditures, indebtedness, restricted payments including cash payments of dividends, and fundamental changes in, or disposition of assets. Certain of these actions may be taken with the consent of the lender. In addition, the credit agreement requires that the Company meet certain financial covenants, namely a minimum tangible net worth measure. As of December 31, 2004 and March 31, 2005, the Company was in compliance with all covenants under the credit facility.

5. Warranty Liability

     Changes in the warranty liability for the three months ended March 31, 2004 and 2005 were as follows:

6. Comprehensive Income

     The Company records all changes in equity during the period from non-owner sources as other comprehensive income or loss, such as unrealized gains and losses on the Company’s available-for-sale securities. Comprehensive income, net of any related tax effects, was as follows:

7. Contingencies

     Legal Matters

     The Company is a defendant in various legal matters arising in the normal course of business. In the opinion of management, the ultimate resolution of these matters is not expected to have a material effect on the Company’s consolidated financial statements as a whole.

10

8. Merger with Cardiac Science

     On February 28, 2005, the Company entered into a definitive agreement to combine with Cardiac Science, Inc, a manufacturer of automated external defibrillators based in Irvine, California. The transaction, which was unanimously approved by the boards of directors of both companies, requires the approval of the Company’s stockholders and Cardiac Science’s stockholders and is subject to regulatory review and other customary closing conditions. The Company anticipates that the merger will close during the third quarter of 2005. To effect the combination, the parties have formed CSQ Holding Company, which is sometimes referred to herein as Newco. Quinton Cardiology Systems and Cardiac Science will be merged with newly formed acquisition subsidiaries of Newco. Upon the closing of the transaction, each outstanding share of the Company’s common stock will be converted to the right to receive 0.77184895 share of common stock of Newco and each outstanding share of Cardiac Science’s common stock will be converted to the right to receive 0.10 share of common stock of Newco. In connection with the transaction, the holders of Cardiac Science’s outstanding senior debt and related warrants have agreed to cancel those securities in exchange for 2,843,915 shares of Newco common stock and a cash payment in the amount of $20 million, pursuant to a note and warrant conversion agreement between Newco, Cardiac Science and such holders. Based on the exchange ratios and the companies’ outstanding shares at February 28, 2005, Newco will have approximately 22.3 million shares of common stock outstanding after consummation of the transaction, including shares issued in connection with the conversion of Cardiac Science’s senior notes and related warrants pursuant to the note and warrant conversion agreement, of which our stockholders will hold approximately 48.7% and Cardiac Science’s stockholders, together with the holders of its outstanding senior debt and warrants, will hold approximately 51.3%. The common stock of Newco, which will be renamed Cardiac Science Corporation at the time of closing, is expected to trade on the Nasdaq National Market under the symbol “CSCX” subject to the approval of the Nasdaq Stock Market. The transaction will be accounted for as an acquisition of Cardiac Science by Quinton Cardiology Systems under the purchase method of accounting in accordance with Statement of Financial Accounting Standards No. 141, “Business Combinations.” Quinton Cardiology Systems will be the acquiring entity for financial reporting purposes based on our review of the criteria for determining the accounting acquirer as set forth in Statement 141. These criteria include but are not limited to; relative share ownership of the combined entity, composition of and ability to elect the board of directors, and the entity from which senior management positions are filled. A majority of Newco’s proposed board of directors will be comprised of current Quinton Cardiology Systems directors. In addition, Quinton Cardiology Systems executives will fill a majority of Newco’s senior management positions, thereby directing policies, strategic direction, and day-to-day operations.

     If the planned merger with Cardiac Science is not completed, the Company would be required to expense the deferred acquisition related costs, which totaled $885,000 at March 31, 2005. In addition, if the Company terminates the merger agreement with Cardiac Science under specified conditions, the Company would be liable for $4.0 million in breakup fees.

     In the event that the transaction with Cardiac Science is consummated, the Company anticipates that Newco will use approximately $20 million of our cash to make the cash payment contemplated by the note and warrant conversion agreement to the holders of Cardiac Science’s senior debt and related warrants.

11

Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations

     You should read the following discussion and analysis in conjunction with our unaudited condensed consolidated financial statements and related notes included elsewhere in this report. Except for historical information, the following discussion contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. All statements other than statements of historical fact made in this Quarterly Report on Form 10-Q, including future results of operations or financial position, are forward-looking. We use words such as anticipate, believe, expect, future, intend and similar expressions to identify forward-looking statements. These forward-looking statements reflect management’s current expectations and involve risks and uncertainties. Our actual results could differ materially from results that may be anticipated by such forward-looking statements. The principal factors that could cause or contribute to such differences include, but are not limited to, those discussed in the section entitled “Certain Factors That May Affect Future Results” below, those discussed elsewhere in this report and those discussed in our Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on March 16, 2005, as amended on Form 10-K/A filed on April 22, 2005. Readers are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date of this report. We undertake no obligation to revise any forward-looking statements to reflect events or circumstances that may subsequently arise. Readers are urged to review and consider carefully the various disclosures made in this report and in our other filings made with the SEC that attempt to advise interested parties of the risks and factors that may affect our business, prospects and results of operations.

     Critical Accounting Estimates

     The discussion and analysis of our financial condition and results of operations are based upon our unaudited condensed consolidated financial statements which have been prepared in accordance with accounting principles generally accepted in the United States of America for interim financial statements. The preparation of these financial statements requires us to make estimates and judgments that affect the reported amounts of assets, liabilities, revenues and expenses, and related disclosure of contingent assets and liabilities. On an ongoing basis, we evaluate our estimates, including those affecting revenues, the allowance for doubtful accounts, the salability and recoverability of inventory, the adequacy of warranty liabilities, the realizability of investments, the calculation of our effective tax rate, the impairment of long-lived assets, the useful lives of tangible and intangible assets and the likelihood of closing a potential business combination for which related transaction costs have been deferred. We base our estimates on historical experience and on various other assumptions that we believe to be reasonable under the circumstances, the results of which form our basis fo